Familial Colorectal Cancer Type X (FCCTX) is a type of hereditary nonpolyposis colorectal cancer in accordance to Amsterdam criteria-1 for Lynch syndrome, with no related mutation in mismatch repair gene. FCCTX is microsatellite stable and is accounted for 40% of families with Amsterdam criteria-1 with a high age of onset. Thus, the carcinogenesis of FCCTX is different compared to Lynch syndrome. In addition to the microsatellite stability and the presence of less predominant tumors in proximal colon, various clinical features have also been associated with FCCTX in comparison with Lynch syndrome such as no increased risk of extra-colonic cancers, older age of diagnosis and higher adenoma/carcinoma rate. Genetic etiology of this type of cancer which is autosomal dominant is unknown. In this review, we focus on the genes and their variants identified in this type of CRC. In order to find out the correlation between FCCTX and various genes database such as PubMed and PMC, search engine such as Google scholar and portals such as Springer and Elsevier have been searched. Based on our literature search, several studies suggest that FCCTX is a heterogeneous type of disease with different genetic variants. Recent studies describe the correlation between FCCTX and genes such as BRCA2, SEMA4, NTS, RASSF9, GALNT12, KRAS, BRAF, APC, BMPR1A, and RPS20. Considering the fact that BRCA2 has the highest mutation rate (60%) and is one of the most crucial DNA repair genes, it will be considered as a big role player in this type of cancer in comparison with other genes.
Keywords: Amsterdam criteria; Familial colorectal cancer type X; Lynch syndrome; Mutation.
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